VERTical EXchange in the Southern Ocean

Mitigating global climatic changes due to human influences is of paramount importance in the coming decades. Historically, the global ocean has played a critical role in this process by taking up the majority of the excess heat and about 30% of the anthropogenic carbon-dioxide (CO2) emissions from the atmosphere. The largest share of this uptake process occurred through the subduction of waters in the Southern Ocean that sequester heat and carbon in deeper layers of the ocean. Yet, global climate models have their largest biases in this region and difficulties in representing its past climatic changes. Thus, their future projections bear large uncertainties in the potential of the Southern Ocean to continuously provide such a mitigation service. VERTEXSO addresses this challenge by studying vertical transport processes, improving their representation in models, and developing novel methods to continuously monitor the vertical exchange. In order to reach these goals, this project performs simulations with a regional ocean model that is able to directly resolve convective plumes and assesses their impact on vertical carbon exchange. We then scale the insights to a global level by improving parameterisations of vertical processes in an Earth System Model, and by investigating their impacts on global climatic changes. Facilitated by most recent advances in remotely observing the Southern Ocean high latitudes, we explore tracers of convective plumes in subsurface data and integrate these observations with satellite data to assess surface density stratification changes. The latter forms a new measure for vertical exchange that serves as a benchmark for model simulations and a tool to monitor the potential of the Southern Ocean to take up and release CO2 and heat. Through this combination of observational data with multi-scale model simulations, VERTEXSO advances the understanding of vertical exchange in the Southern Ocean and how its changes affect the global climate.